ORGANOPHOSPHORUS AND ORGANOCHLORINE PESTICIDE RESIDUES IN SOILS AND UPTAKE BY TOBACCO PLANTS

Abstract

Studies were conducted in 1972 with four organophesphorus insecticides, chlorpyrifos (Dursban®), leptophos (Phosvel®), methidathion (Supracide®) and N-2596 and in 1973 with chlorpyrifos, leptophos and methidathion and one organochlorine, heptachlor, to determine their residues in soils and tobacco (Nicotiana tobacum L.) plants. In 1972, all organophosphorous pesticides were detected in the soil 3 mo after application, but none was detected in cured tobacco leaves. In 1973, ca. 68% of the leptophos applied in June was found in the soil in September, whereas only 20% of the chlorpyrifos and 2% of the methidathion was detected. Heptachlor was persistent in the soil and its conversion product, heptachlor epoxide, was detected in the soil in September but not in June. Gamma chlordane, an impurity in technical heptachlor, was also detected in the soil. In non-cured tobacco, chlorpyrifos and leptophos were detected in sand leaves but not in mid or top leaves. Methidathion was not found. Heptachlor, heptachlor epoxide and γ-chlordane were found in sand, mid and top leaves.